Sram Bottom Bracket GXP ( if you are using this bottom. Bracket with the rotor crankset then you will need a rotor bottom bracket as the SRAM GXP will not work with the rotor spindle. So this quote includes the rotor English bottom bracket)

That's quite a jump in price and performance. Given the weight you'd save in upgrading, I reckon an 11-28 cassette would do you for all but the steepest of steep hills (34 x 28). For the price of a BB I'm with Jimmo62 - get a new one.

Don't forget that you will need to get the WiFli rear deraillure if you want to use a cassette larger than 28T. Personally I run an 11-28 with compacts in Red and I can get up 15% + gradients and I am definitely not the strongest rider in the world. The 11-32 will allow you to spin a bit faster up the hills but you will increase the spacing between gears. This may make it a little harder to get the right gear sometimes. It is really a personal preference in the way you wan to ride. There is nothing wrong with using a 32T cassette if that works better for you.